Stabilized extreme pressure lubricant



STABILIZED EXTREME PRESURE LUBRICANT Paul R. Chapman and Allan A. Manteu tfel, Crystal Lake, and George Wolfram, Des Plaines, Ill., assignors to The Pure Oil (Iompany, Chicago, 111., a corporation of Ohio No Drawing. Application January 13,1956 Serial N0. 553,830

Claims. (Cl. 252*465) Our invention relates to an improved extreme pressure lubricant. More particularly, our invention is directed to an extreme pressure lubricant composition having polymerization-inhibiting and corrosion-inhibiting properties, together with improved storage stability.

Extreme pressure lubricants have found extensive use in the lubrication of gear transmissions of trucks and other vehicles, since this service demands lubricants of special qualities, including high lubricity and high film strength. When a lubricant is compressed between two moving metallic surfaces, high film strength is necessary to prevent the escape or squeezing out of thelubricant from between the surfaces, and consequent welding of the metallic surfaces. The extreme pressures to which such lubricants are subjected when highly compressed between adjacent gear surfaces cause a rise in internal heat which is augmented by any friction generated by a lack of point lubricity. Petroleum lubricating oil fractions, as such, have been found to be unsatisfactory in that they lack requisite high lubricity and high film strength and conse= quently allow scoring and welding of the gears on continued use. Then too, the oil breaks down because of the heat generated by high friction. 7

Such is the case particularly with more or less highly refined lubricating oil fractions which tend to have lower lubricity because of the refining steps to which they have been subjected.

Many types of additives have been prepared and added to extreme pressure lubricant formulations in order to augment film strength, lubricity and other desired charac'- teristics. Fatty oils and fatty acid esters, for example, have been added in various amounts and combinations to hydrocarbon oil fractions to furnish increased oiliness, that is, high lubricity. Sulfur-containing compounds have been added to lubricants to furnish extreme pressure properties, the film strength being somewhat increased thereby, and recent formulations have combined ester additives with sulfur by sulfurizing the esters, thereby iin-' proving both lubricity and film strength of the composi ticir. Still more recently, phosphorus has been incorpo rated in the sulfur-containing ester additives to further augment desired film strength. Oils and fatty esters may have incorporated therein phosphorus and sulfur by reaction With any one of a number of phosphorus sulfide compounds, such as phosphorus sesquisulfide. The in creased performance of such esters in extreme pressure lubricants, When compared with esters containing" only sulphur in similar formulations, maybe seen in that the former are efiective for transmissions opera-ting at low speed and high torque and athigh speed and low torque, whereas esters which have only been sulfurized are etfec due only under conditions of low speed and high torque.

Fatty esters containing sulfur and phosphorus not only increase the extreme pressure properties of the fortun lation, but also exhibit high lubricity and high film streng'th, together: with mil'd'inhib'itionof corrosion stemming from a reduced. tendency for the petroleum base oil to break down. Conse uentlyeludge, acidic corrosive bodies, and

gum-forming compbunas'develop to alesser extent. How; ever, it has been found that the normally slow rate of polymerisation of some fatty esters is accelerated and promoted by the presence of phosphorus in the formulati'o'n, particularly where phosphorus is present together with sulfur. When sulfur alone is present inthe formulation, promotion and ae'celeration of the fatty ester polymerization do not take place. The polymerizationreaction deleteriously affects the'extren'ie pressure lubrican't formulation by producing insoluble materials which tend to clog the ino'viiig parts being lubricated and increasing internal andexter'na'l friction, and therefore increase the instability of thepfe't'roleuni base oil, resulting in increased production of acidicbodies and other deterioration cotnpouhds. Moreover, the added lubricity and film strength supplied by the extreme pressure additive are dissipated through the conversion of the additive in part or in whole into an oil-insoluble, polymerized material. It is, therefore, highl advantageous toelithihat'e'br largely inhibitpol'ymerization in the extreme pressure lubricant during storage and also during use iifidei increased pres sure and/ or increased temperature. I e H It therefore is an object of this i'nvehtioti to "provide for the inhibition of polymerization in a fatty estercontaining extreme pressure lubricant.

It is another object of this invehtioii to iinptiit ssti= corrosion properties, increased stability, filmstreiigtli, and lubricity to an extreme pressure l'ubrie'ar'lt of the fatty ester-type containing phosphorus and sulfur.

It is a furtherobject of. this inveritidri t p rovide-situate stable, extreme pressure lubricant exhibiting polyrr'i I a'- tion inhibition with fg'ai'd to sulfuri'zed-phosphorized fatty esters in the formulation, andalso anti-cohesion properties.

In general, our invention comprises a compds'itiofi iiicorpora-ting a phosphorus-containing fatty ester, or a phosphorus-and-sulfur-containing fatty ester, or a mix ture thereot, inv combination with a polymerizatiomin hibiting' and corrosidndnliibiting agent. More partieu= larly, our invention resides in an extreme pressure lubricat ing-esmpesition comprising a major amount of mineral lubricating oil, a minor amount of a phosphorus-contain ifi'g" fatty ester or a phosphorus-anthsulpbur-containing fattyest'ei', and a polymerization-inhibiting and eorrosion inhrbltifig' a'moulnt of androgen-containing,- fatty acicl= derived; aliphatic hydroxy' eoinpound such as aliphatic" hydroxy amines, aliphatic hydroxy amides and hydroxy= containing aliphatic amine salts of fatty acids with a carbon chain of 16 to 22 carbon atoms.

The base oil in our improved, extreme pr'essuie lu'br'i cant may comprise any petroleum lubricating" oil fra'ct iongsuch as a neutral or bright stockoil of any suitable us: cosity'. Non-limiting examples of said petroleum lubr'itiat ing' oil fractions: are 15 0 SUS-viseosity at 210 F. bright stocl' ,,ancl 170 SUSviseosity and 200 F. viscosity'at F. neutral oils. of said petroleum-lubricating oil fractions as also cdntemplated for use as or in the base oil, for example, esttract. oil from phenol extraction t6 produde I50 viscosity at 21-0" is. bright stdck, wl'iie'h means use are rnati'cextract obtained by smashes with sheet the requisite residualv lubrica g on irac'tin remdving 13 the phenol from the extract ph'a usually under reduced pressure, followed by s'taifi Patented} an. 14, 1958* Aromatic extracts from the mafiutaetute ing oil fractions, and mixtures of said extract oils with said finished lubricating oil fractions.

The extreme pressure additive of our composition is derived from any mono-, di-, or trihydroxy aliphatic alcohol ester of a fatty acid which is soluble in the petroleum base oil utilized in the formulation. The ester preferably is of a fatty acid of 12 carbon atoms or more, and more preferably is one of a fatty acid of 16 carbon atoms or more, for example, palmitic, arachidic, behenic, palmitoleic, petroselinic, vaccenic, linolenic, eleostearic, licanic, parinaric, tariric, gadoleic, arachidonio, cetoleic, erucic, stearic, linoleic and oleic. Other representative fatty acid esters include both saturated and unsaturated types, such as glycerol trioleate, methyl oleate and the dioleate of propylene glycol. Castoroil, lard oil, sperm oil, degras and other fatty materials containing mixed fatty acids and/ or esters also may be used. An especially preferred ester-is the methyl ester of tall oil fatty acids, a commercial form of which is Metalyn, manufactured by the Hercules Powder Company, with the following characteristics:

Percent methyl esters of rosin acids 45.0 (typical). Percent methyl esters of fatty acids 47.0 (typical).

Percent unsaponifiable modified AOCS Ca 6b-40 8.0 max. Saponification No. (drastic Hercules Method) 155/170.- Acid No. (AOCS Da 14-42) 5.0 max. Iodine No. (AOCS Cd 1-25) 120/130. Acetyl value (AOCS Cd 4-40) 10.0 max. Color (Gardner 1933) 12.0 max. Specific gravity 20/20 C .95/.975. Flash point C. (COC) 182 min. Freezing point C 10.0 max. Viscosity at 100 F. SUS (ASTM D445-46T) 70/100. Moisture (AOCS Ca 2a-5) 0.1 max. Appearance at 20/30 C Clear and free of foreign matter.

The alcohol radical of the fatty ester, as mentioned above, may be any mono-, di-, or trihydroxy aliphatic alcohol radical, but it is preferable that the alcohol be a lower molecular weight alcohol, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, allyl alcohol, n-buty alcohol, isoamyl alcohol, sec.-butyl alcohol, tert.-buty alcohol, isobutyl alcohol, isopropyl alcohol, n-amyl alcohol, tort.- amyl alcohol, glycol, glycerol, propylene glycol, trimethylene glycol and the like, whether it contains one, two or three hydroxyl radicals. A fatty ester may be used alone or in combination with other fatty esters. If a mixture 18 used, one or more of the esters may be sulfurized and the other esters may be phosphorized-sulfurized, or alternatively, all the esters may be phosphorized-sulfurized or phosphorylated. An example of a suitable mixture is Metalyn in that it comprises a mixture of methyl esters of the fatty acids of tall oil which contains a mixture of linoleic acid, oleic acid and resin acids, principally abietic acid. The proportions of the constituents fluctuate to some extent from sample to sample.

Thefatty esters may be sulfurized by any one of a number of known methods, including the following: Elemental sulfur in the form of finely powdered sulfur may be sifted in small increments into a kettle containing the fatty ester or fatty ester mixture, for example, Metalyn. The constituents in the kettle are heated to about 275 F. to 285 F. while being vigorously agitated by a mechanical agitator. In the case of Metalyn, it is preferable to react 93 parts of Metalyn with 7 parts by weight of sulfur, but the ratio of Metalyn to sulfur may vary from about 85 parts Metalyn with parts sulfur to about 97 parts Metalyn with 3 parts sulfur. Suitable ratios are known for other fatty ester mixtures. After the addition of the sulfur to the fatty ester, the temperature of the mixture is raised to about 350 F. and the reaction is allowed to proceed for about 7-8 hours until fully completed, as indicated by a corrosivity test, such as a copper strip test. Shorter reaction periods may be employed where active catalysts are available and the fatty esters and sulfur react more quickly. During the final stages of reaction, the temperature may be allowed to rise to about 375 F. to insure complete reaction. The aforesaid copper strip test consists of immersing a copper strip in a sample of the product for one minute at 300 F., and if the copper strip shows a peacock color, the reaction is complete. In the case of Metalyn, the final product may contain about 6.25 percent of sulfur as the preferred quantity, although other fatty esters may contain various amounts, such as 3-10 percent of sulfur. Where smaller amounts of sulfur are desired, the reaction time and/or temperature may be reduced. Conversely, if larger amounts of sulfur are to be incorporated, longer reaction times and/ or higher temperatures will be required to obtain the finished product. However, temperatures in excess of 400 F. should be avoided.

The introduction of phosphorus into the fatty ester may be brought about by reaction of the fatty ester or fatty ester mixture with any suitable phosphorussulfide, such as, phosphorus pentasulfide (P 8 or preferably phosphorus sequisulfide (P 8 the latter containing trivalent phosphorus and forming a complex phosphorusand-sulfur-bearing end-product in which substantially all of the phosphorus in the phosphorus sulfide is present. In the case of phosphorus sesquisulfide, the fatty ester is, for example, mixed in a kettle with the phosphorus sesquisulfide and the mixture is heated to -195 F. with continuous agitation. Then the temperature is increased to 220-230 F., and maintained there for about 4 to 5 hours, or until the reaction with the phosphorus sesquisulfide is complete. Substantially all of the phosphorus and all of the sulfur from the phosphorus sesquisulfide are incorporated in the fatty ester, or the fatty ester mixture, during the reaction period. Under controlled conditions the quantity of phosphorus introduced in the ester may be varied, as may the quantity of sulfur introduced into the ester. Thus, an ester may be treated so as to principally phosphorize it, the relative amount of sulfur introduced being minor in amount.

An example of one procedure is the reaction of glycerol trioleate in amount of 97.5 parts by weight with 2.5 parts by weight of finely divided phosphorus sesquisulfide by mixing at 185 R, which temperature is then raised to 225 F. and maintained there for 4.5 hours under continuous agitation with a mechanical stirrer in a conventional reaction kettle. The end-point is determined by immersion of a copper strip in a sample of the reaction mixture at 210 F. for three minutes. On removal, the strip should show a bright surface. Upon completion of the reaction, the glycerol :trioleate contains both phosphorus and sulfur, the product having a complex structure, as yet not clearly defined. The percentage by weight analysis of the product, for example, may be 1.26 for the phosphorus and 0.97 for the sulfur, but may vary depending upon the reaction conditions.

As mentioned above, combinations of more than one ester, in which one or more of the esters may contain phosphorus with or without sulfur and the remaining esters may contain sulfur with or without phosphorus, are contemplated. Thus, for example, an effective combination is sulfurized Metalyn together with sulfurizedphosphorized glycerol trioleate. This combination is preferred in our composition because it is generally compatible with various petroleum lubricating oil fractions and is of low cost. In the case of the Metalyn-glycerol trioleate combination, it has been found that it is generally undesirable to treat the Metalyn or similar esters with phosphorus sulfide in that the phosphoriza'tion reaction immediately produces some polymerization and decreases the yield of end-product. This situation extends to the methyl esters of tall oil as well as the ethyl,

propyl, butyl and amyl esters, and particularly to the iso- I I v piopyl esters, isobuiyl esters and similar bunch-clam esters. The incorporation of the phosphorus in the fatty ester is therefore preferably performed with fatty esters other than those of the tall oil type. it has been shown that mono-, di-, and trioleates of glycerol exhibit no immediate polymerization upon reaction with the phosphorus sulfide and are therefore preferred fatty esters for reaction with the phosphorus sulfide. The extreme pressure additive produced as outlined above increases the temperature stability, pressure resistivity, lubricity and film strength, and fortifies to some .extent the base .oil against deterioration ,and formation of corrosive bodies. It may be present in any effective minor amount,,such as, for example, percent by weight of the final composition.

The polymerization-inhibiting and corrosion-inhibiting agent of our formulation may be presentin anyreifective minor amount, such as, for example, 0.05-10 percent by weight of the final composition, and comprises .at least one member of the class of compounds characterized as basicorganic nitrogen compounds derived from at least one fatty acid containing a carbon chainlength of at least 16 carbon atoms, preferably ,a mixture of fatty acids in which the major components ,have 16 to .22 carbon atoms. These compounds fall into three sub-classes, the fatty amides, the fatty amines, and the aliphatic amine salts of fatty acids. In each case the basic organic nitrogen compound contains at least one hydroxyl radical. Theadditive must alsobe oil-soluble, or soluble when used in conjunction with a suitable assisting agent which renders it oil-soluble. Mixtures of the abovecompounds also are stipulated as satisfactory as the polymerization-inhibiting and corrosion inhibiting agent.

The fatty hydroxy amines referred to as efiective polymerization-inhibiting and corrosion-inhibiting agents in our formulations may be ,only those amines which contain at least one hydroxyl radical and which have .at least .one carbon chain of 16 22 carbon atoms. The term fatty hydroxy amines indicates, according to current terminology, the fact that the amines were derived from fatty acids of comparable carbon chain length and have at least one hydroxyl group present. Such fatty hydrous 9,1i,l3-octadecatrienylamine; secondary amines such as I'Z-hydroxy octadecylamine; unsaturated hydroxy primary amines, such as, 12-hydroxy-9-octadecenylamine; 12-hydroxy-9,ll-cctadecadienylamine; and 12- hydroxy-9 ,1l, l S-octadecatrienylamine; secondary amines containing at least one hydroxyl gr oup,.such.as N-stearyl- N-ricinoleylamine; hydroxy diamines, such as ,N-stearyl- N'-ricinoleyl-1,3-propanediamines; and tertiary amines containing at least one hydroxyl group such as N-stearyldi (N ricinoleyl 1,3 propanediamine). Other basic nitrogen compounds derived from a fatty acid origin, containing at least one carbon chain of ,16.22 carbon atoms and at least one hydroxyl radical in the molecule, and which are oil-soluble or may be rendered so by an assisting agent, are also contemplated as withinthe scope of our invention.

Many methods may be employed in the preparation'of the desired hydroxy amines. One suitable method in-. volves the following: .A hydroxy fatty acid or mixture thereof, may be reacted with ammonia for the production of the ammonium salt of the fatty acid. When this is heated, it decomposes to a fatty amide whichin turn forms an aliphatic nitrile. Upon "hydrogenation, the nitrile is converted to the desired fatty amine.

The hydroxy amides which may be utilized as polymerization-inhibiting and corrosion-inhibiting agents in the extreme pressure formulations of our invention are of comparable chain length and configuration to the "abovementioned hydroxy amines, for example, l2 hydroxy octadecenyl amide and 'IZ-hydroxy octadec'yl amide. Thus, the hydroxy-amides suitable for the purpose of this assume invention have at least one saturated or unsaturated can [i011 chain of 16 to 22v carbonatoms. The ,unsaturatedl ydroxy amides may have .one or more double :01 i-triple bonds. They may also have more than one hydroxyl radical per molecule. The methods of preparation .are essentially similar to those described abouefor the amines. For example, a hydroxy fatty acid is vreacted with emmonia to form the amine salt which upon heating decomposes to the amide. Thus, the hydroxy amides may be primary, secondary, or tertiary fatty-acid-deri-ved amides, saturated or unsaturated. Each suitable rhydroxy amide is either oil-soluble or issolublein the presence, of a solubility assisting .agent.

The aliphatic hydroxy-contain'ing amine .salts .of fatty acids utilizable for polymerization-inhibiting .and .conrosion-inhibiting agents in the extremepressure formulations may be any such salts which'are comparableto the amines and amides specified above. The amine .p,ortiou Qf'the salt may be a hydroxyl-containing amine .of primary, secondary, or tertiary nature, saturated or ,unsaturated. An example is Duomeen Tmono-ricinoleate, a commercial product made from tallow (principally stearic) ,acids. It is represented by the following formula:

WhereR represents thealkyl radicalsderived fromitallow acids, and-the (C H COO-) group ;r,epre sents :the ?hydroxyacontaining aliphatic ;radi,c, al derivedzfrom ricinolei-c acid, which is of .the formula:

This comp nd m y-b utilizedrin y itable concentration,.such as 0.1% by weight of final composition.

-A CRC-L-ZZ storage stability test and :a shelf storage stability test were run ,on a ,series of extreme :pressure lubricants differing from one another "as to the ipolyrnerizationainhibiting and corrosion-inhibiting additive. lhe following .table ,sets ,forth the results -;of these :tests.

TABLE I BlendNQ.... .1 I

Rementby weight. composition: E. P. base: Sult'urized Metaly-n, 5 parts; phosphorized glycerol tri-i ,Acryloid Bright Stock (150 SUSat 210 Neutral oil (170 SUS at 100 F.). ,Duomeen T Dioleate** Duomeen 'l mono-rieinoleate.--

Viscosities (SUS): 210 F Days 30 Separation ,Light None Light GRCL22. Percentnon-petroleum:

;30 days 0.3/0.5 0.00 0:00

60 days., 0; 00; 1 0:01

120 days o. 00 p.07

*Acryloid 150 is a viscosity index tmprover and pour point depressant It is amethacrylate polymer. SeePatent No. 2,681,891.

*jDuomeen ,I Dioleateis the oi-oleieaeidsalt ota fatty'amine having theiormula:

, Alkyl=lTTOH:-CH: O Ev nt- H in which the alkyl group is a mixture of (31a to Q s'saturated chainszand a 01s mono-unsaturated chain derived from tallow acids. r Y

It is clearly seen from the foregoing table :that in treme pressure lubricant, blend I, showeda light ,separai 7 p tion, whereas blend II showed no separation after one hundred and twenty days and the Duomeen T dioleateprotected blend III showed a light separation after 135 days in the shelf storage stability test. The results were even more dramatic in the CRC-L-22 storage stability test where the percentage of non-petroleum deposits was found to reach a maximum in 60 days in the unprotected oil, while blend II made in accordance with this invention, showed no deterioration up through 120 days. Blend III showed a slight percentage deposit in 60 days of 0.01%, and a slightly greater deposit of 0.07% at the end of 120 days. It is therefore apparent that both Duomeen T diolcate and Duomeen T monoricinoleate are eliective pplymerization-inhibitingagents, and that the latteris distinctly more advantageous than Duomeen T dioleate.

The CRC-L-ZZ test was performed in the following manner: Two centrifuge tubes (100 ml. cone-shaped ASTM designation D96) were rinsed with naphtha, cleaned with concentrated sulfuric acid saturated with sodium or potassium dichromate, rinsed with distilled water, rinsed with 95% alcohol or S-free acetone and air-dried. They were then Weighed to the nearest mg. and 100 ml. of the test lubricant placed in each tube. The tubes were then stored at the desired temperature in a darkened room for 30 days. On conclusion of the storage period, the tubes were centrifuged at 1500 R. P. M. (in a centrifuge of 15-17 in. swing diameter) for minutes, after which the supernatant oil was decanted and the tubes were allowed to drain for 1 hour at room temperature. The solid residue was washed with ASTM naphtha to an oil-free state and dried at 220 F., and the tube weighed to the nearest mg.; where the residue was liquid, it was restored for 60 days, then recentrifuged and the volume of separated liquids observed to the nearest 0.05 ml. Where the separated material was solid, the increase in weight of each tube and residue over the initial weight of the clean tube was reported in terms of percent by weight of the nonpetroleum material originally in the sample. Where the separated material was liquid, the volume was reported in terms of percent by volume of the non-petroleum material originally in the sample.

Blends II and III were then subjected to a series of bench tests, namely, the ASTM turbine oil rust test, the modified SAE machine test and the Timken test.

The turbine oil rust test was performed according to the procedure of test method ASTM D-665-53T, which may be briefly described as follows: A mixture of 300 ml. of the oil under test is stirred with 30 ml. of distilled or synthetic sea water, as required, at a temperature of 140 F. with a cylindrical steel specimen completely immersed therein, usually for a period of 24 hours. The specimen is then withdrawn and examined under normal light without magnification to determine the degree of rusting. A rusted specimen is one on which any rust spot or streak is apparent by visual inspection.

The modified SAE machine test is performed in the following manner: The SAE machine is equipped with a temperature-controlled oil reservoir from which the test lubricant is pumped to the test pieces. The overflow from the upper oil pot returns to the reservoir. The test cups are weighed on an analytical balance before and after the test and the weight loss is used jointly with a visual evaluation of the surfaces to provide a rating on the test oil. Conditions are:

The SAE machine used is the SAE extreme pressure status lubricant testing machine (CRC designation EL-17-545) and consists essentially of a device in which two cylindrical test specimens are rotated in line contact with each other and in opposite directions, with provision for controlling the speed of rotation, the slipping velocity, and the rate of applying pressure at the line contact be tween the rotating cylinders.

The Timken CRC L-18-545 test was used, a brief summary of which follows: The Timken extreme pressure lubricant testing machine (CRC designation EL-18545) is cleaned and about 1 pint of the test lubricant is put into it, circulated through it for 23 minutes, and discarded. Fresh test lubricant at li5 F. then is placed in the machine and circulated therein for 15 minutes prior to the test. The test cup (average surface finish 20-30 micro-inches) is placed on the mandrel, and the test block in the holder on the machine. Test cup and block are then covered with test lubricant. When the apparatus is properly aligned and the reservoir on the machine is about 50% full of lubricant, the machine is started. The mandrel revolves at 800 R. P. M., producing a rubbing speed on the test cup of 400 R. P. M. The desired load is applied to the lever arm of the machine which runs 10 minutes unless scoring occurs earlier. The test is repeated with a new surface of the test block, a new cup, and a heavier load if no scoring occurs. Tests are run until the weight necessary to cause scoring is found. The width of the score on the test block is measured and the load in pounds per square inch at the end of the test can be calculated as follows:

beam load (lb) X 10 scar width (in.) scar length (in.)

The load-carrying capacity of the test lubricant is reported as the pressure, in pounds per square inch held by the test lubricant at the end of a ten minute test period during which the maximum load which will not cause seizure, or scoring, is applied to the machine.

The results of the above tests with blends l1 and III Pounds per square inch The function of dibenzyl disulfide in the formulations set forth in Table I is to provide additional, properly available sulfur in the extreme pressure lubricant to assure satisfactory load carrying performance of the lubricant at low temperatures and pressures.

The corrosion-inhibiting characteristics of the polymerization-inhibiting additive of our compositions are set forth in Table HI, which illustrates the results of testing blend II formulation and Duomeen T dioleate (blend IH formulation) by means of the NRL static water drop tester, as set forth in MIL, P-P-17272 (Ships) July 18, 1952. A summary of this test is as follows: The test specimen inch cold-rolled steel, SAE 1020, in the form of an equilateral triangle) is polished on its dimpled side with sandpaper and placed into pure benzene, swabbed with clean gauze, placed into more pure benzene and boiled 3-4 minutes, put into petroleum ether, and boiled 1 minute. The test specimen is immersed with the concave side of its dimple uppermost in a beaker containing oil so that the latter covers it to about 0.25 inch depth. The beaker containing the oil and the sample is heated to :t.2 F. for 1 hour and removed. A drop of water, 0.2 ml., is placed in the oil so as to rest in the dimple of the specimen, then the j beaker is stored at l40i2 F. and observed daily for failure of the specimen, i. e., the first sign of rust which increases in intensity the following day. Four test specimens are run. Where the water drop slowly disappears, 1t-is restored by adding more water to reachits original' TABLE III Blend number II III In summation, it has been found that, contrary to expectations, when about 0.1 percent by weight of the basic nitrogen-containing polymerization-inhibiting and corrosion-inhibiting additive of our invention is added to a lubricant incorporating a fatty ester or a mixture of fatty esters which have been phosphorized and/or phosphorized-sulfurized, the promotion of polymerization of said fatty ester, or esters thought to be brought about by the presence of phosphorus, particularly phosphorus together with sulfur, is counteracted so that satisfactory stability of the lubricant is achieved. Furthermore, extreme pressure lubricants containing the above-mentioned constituents incorporated in a mineral oil fraction exhibit corrosion inhibition. The polymerization-inhibiting and the corrosion-inhibiting characteristics of the formulation are present both during storage of the lubricant and during use of the lubricant under conditions of extreme pressure and elevated temperatures.

The constituents of our composition may be added together in any suitable manner, that is, with or without stirring, in conventional apparatus, and in any sequence; the constituents may be added intermittently, continuously, swiftly or slowly, in any manner to achieve a homogeneous extreme pressure lubricant.

In addition, the composition of our invention which comprises a petroleum base oil, together with the extreme pressure and the polymerization-inhibiting and corrosion-inhibiting additives indicated, may include other conventional lubricating oil additives in the composition for known specific properties, and which do not substantially interfere with the extreme pressure characteristics, polymerization-inhibition, or corrosion-inhibition. Such additional additives may be viscosity index and pour point improvers, such as Paratone, a polyisobutylene polymer; Acryloid, polymers of the esters of methacrylic acid and higher fatty alcohols; Santodex, an alkyl styrene polymer; Paraflow, a complex condensation product of parafiin wax and naphthalene; Santopour, a paraffin wax-phenol condensation product; and foam depressants, such as Dow Corning Fluid DC-ZOO, a silicone polymer, and Monsanto Chemical Companys PC4308.

The sulfurized Metalyn and phosphorized glycerol trioleate used in blends I, ll and III, Tables I, II and III were made in the manner specifically set forth earlier in this specification.

We claim and particularly point out as our invention:

1. An extreme pressure lubricant which comprises a mineral oil, an extreme pressure additive comprising at least one phosphorized and sulfurized ester of a fatty acid and aliphatic alcohol, in amount sufficient to enhance the load-carrying properties of the oil, and a nitrogen-containing compound comprising at least one substance of the group consisting of aliphatic hydroxy amines having at least one carbon chain of at least 16 carbon atoms, aliphatic hydroxy amides having at least one carbon chain of at; least 16 carbon atoms and aliphatic. hydroxy aminesalts, having at least, one carbon chain; of at least 16 carbon atoms, of fatty acids, said sub} stance being present in an amount sufficient to improve the storage stability of said lubricant. v

2. An extreme pressure. lubricant which comprises a major amount of a petroleum lubricating oil, an amount suflicient to impart extreme pressure properties to the said lubricating oil of a mixture of esters of fatty acids of carbon chain lengths of at least 12 carbon atoms and lower aliphatic alcohols, which have been sulfurized and phosphorized with phosphorus sesquisulfide, and a nitrogen-containing compound comprising at least one substance of the group consisting of fatty hydroxy amines having at least one chain of 16-22. carbon atoms, fatty,

hydroxy amines having at least one chain of 16,-22 carbon atoms, and'hydroxy-containing aliphatic amine salts having at least one chain of 16-22 carbon atoms, of fatty acids, said substance being present in an amount sufficient to improve the storage stability of the lubricant.

3. An extreme pressure lubricant which comprises a major amount of a petroleum lubricating oil, sulfurized esters of tall oil and a lower aliphatic alcohol, and an ester of a fatty acid of carbon chain length of at least 16 carbon atoms and a trihydroxy alcohol, which has been chemically reacted with phosphorus sesquisulfide, the latter two components being present in an amount 'sufiicient to impart extreme pressure properties to the oil. and at least about 0.05 percent by weight of the total composition, sufficient to inhibit polymerization, of a nitrogen-containing compound comprising at least one member of the group consisting of fatty hydroxy amines having at least one chain of 16-22 carbon atoms, fatty hydroxy amides having at least one chain of 16-22 carbon atoms, and hydroxy-containing aliphatic amine salts, having at least one chain of 16-22 carbon atoms, of a fatty acid.

4. An extreme pressure lubricant which comprises a mineral oil in major amount, an amount sufficient to impart extreme pressure qualities to said mineral oil of at least one phosphorized and sulfurized ester of a fatty acid of carbon chain length of at least 12 carbon atoms and a lower aliphatic alcohol, and an aliphatic hydroxy amine having at least one carbon chain of 16-22 carbon atoms in an amount suflicient to inhibit sediment formation in the composition.

5. An extreme pressure lubricant which comprises a petroleum lubricating oil in a major amount, an amount sufiicient to impart extreme pressure qualities to said petroleum lubricating oil of at least one phosphorized and sulfurized ester of a fatty acid of carbon chain length of at least 12 carbon atoms and a lower aliphatic alcohol, and an hydroxy-containing aliphatic amine salt, having at least one carbon chain of 16-22 atoms, of a fatty acid, in an amount sufiicient to inhibit sediment formation in the composition.

6. The lubricant of claim 5 in which said hydroxy-containing aliphatic amine salt is an hydroxy-containing aikyl-substituted trimethylene diamine salt of a fatty acid.

7. The lubricant of claim 6 in which the amine salt is the mono-ricinoleic acid salt of a fatty amine having the formula:

where the alkyl group is a mixture of C to C saturated chains and a C mono-unsaturated chain, derived from tallow acids.

8. An extreme pressure lubricant which comprises a petroleum lubricating oil in a major amount, an amount sufficient to impart extreme pressure qualities to said hydrocarbon petroleum lubricating oil of at least one phosphorized and sulfurized ester of a fatty acid of carbon chain length of at least 12 carbon atoms and a lower aliphatic alcohol, and an hydroxy aliphatic amide having 11 at least one carbon chain of l6-22 carbon atoms in an amount sufiicient to inhibit sediment; formation in the composition.

9. An extreme pressure lubricant which comprises a major amount of petroleum lubricating oil, a minor extreme-pressure-imparting amount of an additive which comprises sulfurized methyl esters of tall oil and glycerol trioleate phosphorized-sulfurized with phosphorus sesquisulfide, in a ratio of one to ten parts of sulfurized tall oil esters to one part of phosphorized and sulfurized glycerol trioleate, and a minor amount of IZ-hydroxyoctadecylamine sufficient to inhibit polymer formation.

10. An extreme pressure lubricant which comprises a major amount of a petroleum lubricating oil, a minor extreme pressure-imparting amount of an extreme pressure additive which comprises sulfurized methyl esters of tall oil and glycerol trioleate phosphorized-su-lfuriaed with droxy-octadecylamide sufiieient to inhibit polymer formation.

References Cited in the file of this patent UNITED STATES PATENTS 2,113,150 Wiezevich Apr. 5, 1938 2,268,608 McNulty Ian. 6, 1942 2,628,940 Cyphers Feb. 17, 1953 2,631,131 Waugh Mar. 10, 1953 FOREIGN PATENTS 672,875 Great Britain May 28, 1952 U. 3. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2 820313 January 14, 1958 Paul R, Chapman et ala It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 44, strike out "hydnoxy,ll,lB-OQtadeoatrienylamine; secondary amines" and insert instead --=hydroxy amines are saturated, hydroxy primary amines n Signed and sealed this 25th day of March 19580 (SEAL) I 'Atteet: KARL Ha AXLINE I ROBERT C. WATSON Attesting Officer Conmissioner of Patents 

1. AN EXTREME PRESSURE LUBRICANT WHICH COMPRISES A MINERAL OIL, AN EXTREME PRESSURE ADDITIVE COMPRISING AT LEAST ONE PHOSPHORIZED AND SULFURIZED ESTER OF A FATTY ACID AND ALIPHATIC ALCOHOL, IN AMOUNT SUFFICIENT TO ENHANCE THE LOAD-CARRYING PROPERTIES OF THE OIL, AND A NITROGEN-CONTAINING COMPOUND COMPRISING AT LEAST ONE SUBSTANCE OF THE GROUP CONSISTING OF ALIPHATIC HYDROXY AMINES HAVING AT LEAST ONE CARBON CHAIN OF AT LEAST 16 CARBON ATOMS, ALIPHATIC HYDROXY AMINES HAVING AT LEAST ONE CARBON CHAIN OF AT LEAST 16 CARBON ATO MS AND ALIPHATIC HYDROXY AMINE SALTS, HAVING AT LEAST ONE CARBON CHAIN OF AT LEAST 16 CARBON ATOMS, OF FATTY ACIDS, SAID SUBSTANCE BEING PRESENT IN AN AMOUNT SUFFICIENT TO IMPROVE THE STORAGE STABILITY OF SAID LUBRICANT. 